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O1051 CAN WE RELY ON MAGNETIC RESONANCE IMAGING WHEN EVALUATING UNSTABLE ATLANTOAXIAL SUBLUXATION?



Abstract

Aims: To examine whether functional radiography and functional magnetic resonance imaging (MRI) are equal to detect the extent of unstabile anterior atlantoaxial subluxation (aAAS) in rheumatic patients. Methods: The series consisted of 23 patients with unstable aAAS (diagnosed by functional radiography) examined by functional MRI because of a neck symptom. Twenty-two patients had rheumatoid arthritis and one had juvenile idiopathic arthritis. aAAS was diagnosed if the anterior atlanto-axial diameter (AAD) was > 3 mm and was considered unstable if the AAD differed > 2 mm between flexion and extension radiographs. The AAD was measured from radiographs (flexion and extension) and MRI images (flexion and neutral). Results: The extent of aAAS during flexion measured by radiography was greater than that found by MRI in all our 23 cases [the mean difference was 3 mm (95% CI: 2 to 4)]. In 4 patients (17%) MRI could not find aAAS. The difference between the AAD measurements during flexion by these two methods was substantial (i.e. , ≥ 4 mm) in 9 cases (39%). Severe aAAS (≥ 9 mm) was seen in 15 patients (65%) by functional radiography and in 4 (17%) by functional MRI. Conclusions: The magnitude of aAAS was often substantially smaller in functional MRI than in functional radiography. Thus one cannot rely on functional MRI alone; functional radiographs are needed to show the size of unstable aAAS.

Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.